Producing electrodes for lead acid batteries

ABSTRACT

A system for producing electrodes for lead-acid batteries is disclosed. An electrode that has been produced comprises at least one upper and/or one lower frame element as well as a lattice-shaped region that extends away from said upper or lower frame element and has a plurality of openings, the upper and/or lower frame element being of a greater thickness than the lattice-shaped region. Said system comprises the steps of: a) producing a profiled strip-shaped blank using a casting method in which the strip-shaped blank is formed, solely by means of said casting method, to have a greater thickness on one side in at least one of the regions which should eventually form the upper or lower frame element, than the thickness in regions which should eventually form the lattice-shaped region, and b) producing said lattice-shaped region with the openings in a subsequent expanded metal process.

In general, the invention relates to the field of manufacturing electrodes for lead-acid batteries, particularly negative electrodes. There have already been proposals made, e.g. in EP 1 366 532 B1 or DE 1 02 09 1 38 B4, for using an extrusion press machine to continuously manufacture a lead alloy strip. However, extruding machines of this type are relatively complex and in particular require an extruder.

The invention is based on the objective of specifying simplified possibilities for manufacturing electrodes for lead-acid batteries which can be realized more economically.

The objective is accomplished by a method for manufacturing electrodes for lead-acid batteries in accordance with claim 1, wherein a produced electrode has at least one upper and/or one lower frame element as well as a meshed region extending away from the upper and/or lower frame element and comprising a plurality of openings, whereby the upper and/or the lower frame element is thicker than the meshed region, said method comprising the steps of:

-   a) producing a profiled strip blank in a casting process, wherein     only by means of the casting process is the strip blank formed to be     thicker on one side in at least one of the regions which will     ultimately form the upper or lower frame element than in the regions     which are to ultimately form the meshed region, -   b) producing the meshed region having the openings in a subsequent     expanded metal process.

The invention has the advantage of being able to produce robust electrodes for lead-acid batteries at particularly low manufacturing cost. Designing the upper and/or lower frame element to have a greater thickness produces electrodes which are more mechanically robust than is the case with conventional manufacturing processes. This is in turn made possible by the producing of a profiled strip blank, which known casting methods would enable. In particular, the relationship between electrode quality and manufacturing cost becomes considerably more favorable. The method according to the invention is particularly advantageous even given higher raw material costs, e.g. for the lead, since there is no punching waste in the expanded metal process as created in punching processes. There is thus also no expense for subsequent collection and recycling of punching waste as it is never created in the first place. The combination of the expanded metal process and the casting process, particularly without an extruding step, enables electrodes to be manufactured particularly quickly, which has the advantage of being able to use existing machines particularly efficiently.

The electrode can be configured either with only an upper frame element, with only a lower frame element or with an upper frame element and a lower frame element. When the electrode has both the upper as well as the lower frame element, one advantageous embodiment provides for the meshed region to extend from the upper to the lower frame element. The manufacturing process allows the electrode to initially be produced with both the upper and the lower frame element as need be and then ultimately, particularly after carrying out the expanded metal process, one of the frame elements to be cut away. This gives the electrode increased robustness during the manufacturing process which is conducive to said manufacturing process. Additionally, there is a material savings in the end due to cutting away a frame element.

The strip blank formed in the casting process is thicker on one side in the regions which will ultimately form the upper and/or lower frame element of greater thickness than in the regions which will ultimately form the meshed region. In one advantageous configuration, the upper side of the blank as it exits from the casting process is thereby substantially planar; i.e. smooth, while its underside exhibits a profile comprising the regions of less and the regions of greater thickness. In so doing, a profiled strip blank can be produced without the need for an extruder.

The resulting electrode is also asymmetrical; i.e. it exhibits a greater thickness on one side in the region of the upper and/or the lower frame element than in the meshed region. This results in material savings in the meshed region, which leads to more favorable manufacturing costs and to lower weight.

According to one advantageous further development of the invention, the casting process is a continuous casting process in which the strip blank is produced continuously. The continuous casting process allows the economical and time-saving manufacture of basically any length of strip-shaped blanks and thus the economical manufacture of the battery electrodes at high production speed and high quantities.

According to one advantageous further development of the invention, the electrodes are manufactured without an extruding step; i.e. without using an extruder.

According to one advantageous further development of the invention, the strip blank produced in the casting process is of lesser width than the width of the electrode resulting after the expanded metal process.

According to one advantageous further development of the invention, the region of the strip blank which is ultimately to form the meshed region initially has no openings in step a).

According to one advantageous further development of the invention, it is provided for cutting blades to first provide longitudinal slots in the strip blank in the area of the meshed region to be produced during the expanded metal process; i.e. slots extending in the longitudinal direction of the blank, and to thereafter produce the meshed region by drawing the slotted blank transverse to the direction of the longitudinal extension of the upper and/or lower frame element. If the slotted blank exhibits both the lower as well as the upper frame element at this point in time, the meshed region can be produced by drawing of the slotted blank in that the upper and the lower frame element are pulled apart in opposite directions. This exerts a tensile force on the slotted blank in a direction transverse to the longitudinal direction, which ultimately leads to the meshed region being formed with rhombic openings.

According to one advantageous further development of the invention, the strip blank is produced with at least one first, one second and one third region each extending in the longitudinal direction of the strip blank, at least one of which is of greater thickness, and closed material areas without openings and of lesser thickness are produced between each first and second as well as between each second and third region. Particularly the regions of increased thickness can hereby be asymmetrically formed on one side and this done in the course of producing the profiled strip blank in the casting process. No extruder is required here as well. Advantageously, to save material, only e.g. the second (middle) region can be of increased thickness. All three regions; i.e. the first, second and third region, can also for example be formed with increased thickness.

According to one advantageous further development of the invention, electrode contact tabs are produced out of the second region of increased thickness; e.g. by punching out specific excess areas of the second region. This has the advantage of the electrodes being able to be continuously produced as quasi double-band electrodes and the casting process thereby already integrating the material for the contact tabs at the same time. According to one advantageous further development, the second region of increased thickness is situated between first and the third region of increased thickness.

According to one advantageous further development of the invention, a strip-shaped electrode assembly, which is wound into a coil, is produced from the strip blank in a continuous expanded metal process. A coil is to be understood as a helically wound object. This has the advantage of the electrodes already being able to be largely prepared for later use in batteries, including realizing the expanded metal process. The electrode assembly is comparatively more sensitive to mechanical influences after the expanded metal process being realized. It is therefore advantageous for the already drawn strip-shaped electrode assembly to be wound into a coil. The strip-shaped electrode assembly is less sensitive to mechanical influences in this coiled form and can additionally be easily used for further production steps in the manufacturing of batteries.

The non-profiled flat side of the electrodes can be on the outside when coiling. According to one advantageous further development of the invention, the non-profiled flat side of the electrodes is on the inside during coiling. By so doing, the coiled electrode assembly can be stored so as to be particularly insensitive to mechanical influences.

According to one advantageous further development of the invention, the strip-shaped electrode assembly is first pasted with a pasty active material and then wound into a coil.

According to one advantageous further development of the invention, the electrode is pasted with pasty active material after the expanded metal process and, when applicable, prior to detaching from the strip-shaped electrode assembly. The electrode can thereafter be provided with separator material and inserted into the housing of a lead-acid battery so as to ultimately produce a lead-acid battery.

According to one advantageous further development of the invention, the electrode is initially stored prior to being pasted with the pasty active material and the pasting process conducted after a storage period. This has the advantage of being able to divide the sub-processes of “production of raw electrodes” and “finalizing electrochemically active electrodes” into separate steps which can be realized independently of each other, particularly at different times. Since the two method steps can be realized at different speeds, a suitable dissociating can thereby be made between the sub-processes which allows adapting the overall manufacturing process to the speed of the sub-processes.

According to one advantageous further development of the invention, the electrodes can be stored in coil form.

The objective cited at the outset is further accomplished by a system for manufacturing electrodes for lead-acid batteries, whereby the system is configured to realize a method in accordance with any one of the preceding claims, wherein an electrode produced with the system exhibits at least one upper and/or one lower frame element as well as a meshed region extending away from said upper and/or lower frame element which comprises a plurality of openings, wherein the upper and/or lower frame element is thicker than the meshed region, with the system components of:

-   a) a casting system designed to produce a profiled strip blank to be     thicker on one side in the regions which are to ultimately form the     upper and/or lower frame element than in the regions which are to     ultimately form the meshed region, -   b) an expanded metal press designed to produce the meshed region     having the openings by way of an expanded metal process.

The system can be designed without an extruder.

The objective cited at the outset is additionally accomplished by an electrode manufactured in accordance with one of the above described methods. The electrode can be used in a lead-acid battery as a positive or a negative electrode.

The objective cited at the outset is further accomplished by a lead-acid battery having one or more of the above-cited electrodes.

The following will reference the drawings in describing embodiments of the invention in greater detail.

Shown are

FIG. 1 the production of a strip-shaped blank,

FIG. 2 an electrode,

FIG. 3 a lead-acid battery, and

FIG. 4 a system for manufacturing electrodes for lead-acid batteries.

The figures use the same reference numerals for elements which correspond to one another.

FIG. 1 shows a casting system 1 which produces a strip-shaped blank 2 for electrodes of lead-acid batteries by means of a continuous casting process. The casting system 1 is supplied with lead on the input side (not shown). The casting system 1 melts the lead and dispenses the strip blank 2 as a continuous profiled mold in the extruded form shown in FIG. 1 on the output side. The strip blank 2 can then be further processed as described below.

The distinctiveness of the casting system 1 according to FIG. 1 is that the strip blank 2 can be produced with a profile on one side such that the blank 2 exhibits different thicknesses D across its width B. It can be seen from FIG. 1 that the blank 2 exiting the casting system 1 has a substantially flat, smooth upper side 8 and a profiled underside. The blank 2 comprises regions 3, 5, 7 of greater thickness D than the regions 4, 6 situated therebetween. The regions 3, 5, 7 of greater thickness D project above regions 4, 6 on the underside. On the right, FIG. 1 shows a section of the strip blank 2 turned 180° about its longitudinal axis to show the profiled underside more visibly, illustrating the one-sided profile structure of the strip blank 2 extending in longitudinal direction L.

Depending on embodiment, it is also conceivable for only the middle region 5 to exhibit increased thickness D.

The casting machine 1 is thereby configured wholly without an extrusion unit; i.e. it effects purely a casting process without an extruding step.

As will be described below, the regions 4, 6 of lesser thickness will be trans-formed into the meshed region by an expanded metal process, the upper and the lower frame element as well as part of the electrode contact tabs will be produced from the regions 3, 5, 7 of greater thickness.

FIG. 2 shows a top plan view of an electrode 14 subsequent the expanded metal process in FIG. 2a . To illustrate the relationship to the strip blank 2, the electrode 14 is depicted with additional electrodes which are only partially reproduced at lower contrast or by dotted lines.

As can be recognized, the electrode 14 comprises an upper frame element 10 with a contact tab 11 formed thereon, a lower frame element 9 and a meshed region 12 extending between the upper and the lower frame element 9, 10. To illustrate the relationship to the strip blank 2 according to FIG. 1, the corresponding reference numerals for the regions of the blank 2 from FIG. 1 are additionally reproduced.

The arrows shown in FIG. 2a respectively pointing away from the upper frame element 10 and the lower frame element 9 indicate the direction of the drawing force to act on the electrodes 14 in the expanded metal process.

Individual electrodes 14 are detached from the electrode strip exiting after the expanded metal process by individual electrodes being cut out, as represented by the triangles 13 in FIG. 2a . Correspondingly, the contact tabs 11 are also detached from the upper frame element 10 of the respective oppositely situated electrode. The interstices 15 between the contact tabs 11 are produced by die cutting.

FIG. 2 shows a side view of the produced electrode 14 on the right in FIG. 2b , from which the profiled structure is recognizable.

FIG. 3 shows a lead-acid battery 30 comprising a plurality of electrodes 14 of the type described above. The lead-acid battery 30 comprises a cover part 33 having external terminals 31, 32. The external terminals 31, 32 are respectively connected to positive/negative electrodes via the respective electrode connector 35, 36. For example, the connection of a negative electrode connector 35 to a contact tab 11 of an electrode 14 which in the present case is used as a negative electrode is recognizable. The negative electrode connector 35 is connected to the further negative electrodes and to terminal 31. Analogously, the positive electrode connector 36 is connected to the contact tabs of the positive electrodes 39 and to the other terminal 32.

The lead-acid battery 30 comprises a lower housing part 34 in which the electrodes 14, 39 are disposed. The electrodes 14, 39 are provided with a pasty active material 37. The electrodes 14, 39 together with the pasty active material 37 are additionally respectively enveloped by a separator material 38.

FIG. 4 shows an example of a system for manufacturing electrodes for lead-acid batteries of the type described above. The casting system 1 is again recognizable as the first system component. The above-described strip blank 2 exits from the casting system 1. The strip blank 2 is fed to an expanded metal press 40 which represents the second system component. The expanded metal press 40 first comprises a cutting unit which for example has cutting blades attached to a rotary roller. The cutting blades cut short longitudinal slots, e.g. just a few millimeters in length, into the strip-shaped blank in regions 4, 6. After the strip blank has passed through the cutting unit, it is fed to a drawing device of the expanded metal press 40. The drawing process is realized in the drawing device by the frame elements 9, 10 being pulled apart in opposite directions as shown in FIG. 1 by the arrows of FIG. 2 a.

Lastly, the blank is fed to a punching section in the expanded metal press 40 in which the clear regions 15 between the contact tabs 11 are punched out. The electrode strip 41 ultimately exiting the machine 40, as depicted in FIG. 4, corresponds to the electrode strip as described with reference to FIG. 2. 

1.-10. (canceled)
 11. A system (1, 40) for manufacturing electrodes (14) for lead-acid batteries (30), wherein an electrode (14) produced with the system (1, 40) exhibits at least one upper and/or one lower frame element (9, 10) as well as a meshed region (12) extending away from said upper and/or lower frame element (9, 10) and comprising a plurality of openings, wherein the upper and/or lower frame element (9, 10) is of greater thickness (D) than the meshed region (12), and having the system components of: a) a casting system (1) designed to produce a profiled strip blank (2) exhibiting a greater thickness (D) on one side in at least one of the regions (3, 5, 7) which are to ultimately form the upper and/or lower frame element (9,10) than in the regions (4, 6) which are to ultimately form the meshed region (12), b) an expanded metal press (40) designed to produce the meshed region (12) having the openings by way of an expanded metal process.
 12. An electrode (14) manufactured in accordance with claim
 11. 13. A lead-acid battery (30) having one or more electrodes (14) in accordance with claim
 12. 14. The system according to claim 11, characterized in that the expanded metal press (40) comprises cutting blades that first provide longitudinal slots in the strip blank (2) in the region (4,6) of the meshed region (12) to be produced during the expanded metal process.
 15. The system according to claim 11, characterized in that contact tabs (11) of electrodes (14) are produced out of the second region (5) of increased thickness (D) by die cutting with the expanded metal press.
 16. The system according to claim 11, characterized in that the casting system is a continuous casting system producing a continuous strip blank (2). 